Currently, the wave-activated power generator is practically used as a wave-activated power generating buoy of a nautical mark. An example of wave-activated power generating buoy is shown in FIG. 1. As shown, a wave-activated power generating buoy 1 includes a pipe 3 which is immersed vertically downward with respect to the water surface. The pipe 3 has a bottom end 4 opened downwardly and there is formed an air chamber 2 together with the water surface in the vicinity of a top end of the pipe. Above the air chamber 2 is provided a valve chamber 5, whose interior is divided into an upper chamber 5a and a lower chamber 5b, and an air turbine 6 and a power generator 7 driven by the air turbine 6 are provided inside of the upper chamber 5a. On the other hand, in the side walls of the upper chamber 5a and lower chamber 5b of the valve chamber 5 are provided an appropriate number of valves 8 to be capable of being open and closed. The upper chamber 5a is communicated to the lower chamber 5b via a through-hole 5c. Thus, as the water surface inside of the pipe 3 moves up and down due to wave motion, the air inside of the air chamber 2 flows into the atmosphere through the lower chamber 5b and the upper chamber 5a as indicated by the arrow in FIG. 1, whereby this air flow is utilized to rotate the air turbine 6 thereby driving the generator 7 to generate power.
FIG. 2 shows a performance curve of the wave-activated power generating buoy 1 shown in FIG. 1. In the graph of FIG. 2, the ordinate is taken for specific pressure (peak pressure in the air chamber/wave height) and the abscissa is taken for period (second). As is obvious from the graph of FIG. 2, this performance curve includes two peaks A and B. A smaller period T.sub.A for the peak A is a period of vertical vibration of buoy 1; whereas, a longer period T.sub.B for the peak B is a period of vibration of the water column inside of the central pipe 3 determined by the length 1 of central pipe 3 as ##EQU1## Actual generation of power by the buoy 1 is carried out by the waves between these two periods
In order to implement practical wave-activated power generation, it is necessary to carry out power generation by the waves of broader range of period. And, for this purpose, it is necessary to make the period T.sub.B larger by making the length 1 of central pipe 3 longer. However, if the length 1 of the central pipe is made too long, it cannot be provided in a shallow sea and there are brought about problems in handling and maintenance since it becomes a lengthy structure. Accordingly, there has been a need to develop a wave-activated power generator capable of implementing wave-activated power generation for waves of a broader range of period without bringing about these various problems.
Therefore, the present invention has its object to provide a wave-activated power generator which has obviated the drawbacks of the prior art as described above.
Another object of the present invention is to provide a buoy-type wave-activated power generator capable of implementing wave-activated power generation at high efficiency even in a shallow sea.
A further object of the present invention is to provide a wave-activated power generator which is easy in handling and maintenance.
A still further object of the present invention is to provide a wave-activated power generator capable of implementing wave-activated power generation stably.